The present invention relates to a fastening structure between a link and a pin of a crawler belt in a vehicle such as a construction machine.
A crawler belt utilized in a construction machine, such as a bulldozer and a hydraulic shoveling machine, comprises an endless annular link chain provided with shoes (crawler shoes) for contact with ground. The link chain has such a structure that a plurality of links are interconnected by pins. A structure of the link interconnection is shown in FIG. 8. As shown in this figure, the link chain includes a predetermined number of link pairs of a left-hand and a right-hand links 31, 32 disposed in a longitudinal direction. In each of the link pairs 31, 32, a pin 33 and a bushing 34 fasten an end portion of a longitudinally preceding link pair to a front portion of the following link pair. More specifically, the pin 33 is inserted into the bushing 34, and the bushing 34 is press-fitted into rear holes 41a, 42a of the preceding links 31a, 32a, whereas the pin 33 is press-fitted into front holes 41b, 42b of the following links 31b, 32b. Since the bushing 34 and the pin 33 are pivotable, the preceding and the following links 31a, 31b are connected with each other in a bendable manner like a joint. It should be noted here that, in FIG. 8, a portion indicated by numeral 35 is a lubricating oil supplying hole. Lubricating oil supplied here provides lubrication between the pin 33 and the bushing 34.
According to the crawler belt described as above, the pin 33 is subjected to a large force in a direction of thrust during use. Therefore, according to the link chain described as above, a retaining mechanism for preventing the pin 33 from coming out of the links 31, 32 is provided (for example, U.S. Pat. No. 4,618,190). According to this fastening structure between link and pin, an annular recess is formed around an opening of the pin insertion hole in the link. Further, close to an end portion of the pin, a circumferential groove smoothly recessing in an axially inward direction is formed. The recess in the link and the groove in the pin form a cavity having an annular opening, between the circumferential edge of the opening of the pin insertion hole and the outer end portion of the pin. Into this cavity, there is driven an annular retainer made of a metal for preventing the pin from coming out. The retainer is plastically deformed to conform to the shape of the cavity, so as to fill the cavity with the retainer, thereby preventing the pin from relative, disengaging movement out of the link toward the side away from the opening.
Now, with the above described fastening structure between link and pin, in order to prevent development of an excessive play between the link and the pin, the plastic deformation of the retainer must be carried out sufficiently so that the retainer is tightly fitted to conform to the shape of the annular cavity. However, in order to achieve this, there is a need for complex machining operation, and a high dimensional accuracy in the product. In addition, the recess of the link and the groove of the pin must be aligned with each other accurately, which leads a problem of increased cost of facility and equipment as well as cost of manufacture.
In an attempt to solve the above described problem, the Japanese Patent Application No. Hei 11-182264, for example, proposes a fastening structure of link and pin, in which a retaining ring 36 is employed. Specifically, as shown in FIG. 9, an annular space 45 is formed between a circumferential edge of an opening of pin insertion holes 41b, 42b of the links 31, 32 and a corresponding end portion of a pin 33. The retaining ring 36 is disposed in this space 45, thereby preventing the relative, disengaging movement of the pin 33 toward the side away from the opening. In this case, there is formed a tapered inner surface 43 having a diameter gradually increasing from the pin insertion hole 41b toward outside, surrounding the opening of the pin insertion hole 41b. On the other hand, the pin 33 is formed with a tapered outer surface 44 facing the tapered inner surface 43. A slanting angle of the tapered outer surface 44, with respect to the axis, is slightly smaller than a slanting angle of the tapered inner surface 7. With this arrangement, the tapered surfaces 43, 44 are farther away from each other in the outward direction. The retaining ring 36 is made of an annular elastic metal having a circular section, with a part of the ring cut out so that the ring can elastically spread and shrink in diameter.
However, the above described fastening structure between link and pin of a crawler belt has the following problems resulting from that the opening portion of the pin insertion hole 41b of the link 31 and the outer end portion of the pin 33 are tapered surfaces 43, 44 respectively, and that the retaining ring 36 has a circular section. Specifically, first, assembling operation is costly. More specifically, since the section of the retaining ring 36 is circular, the ring circumferential surface cannot have a sufficient area of contact with each of the tapered surfaces 43, 44, being unable to obtain sufficient initial friction from the elastic restoring force of the retaining ring 36 alone. For this reason, in an assembling step, an operation of driving the retaining ring 36 inwardly is necessary. For this particular operation of driving the retaining ring 36, a special jig dedicated to the pressing operation must be prepared. Further, a pressing apparatus capable of providing a necessary level of driving force is necessary. As a result of these, a high cost is required for the assembling operation.
Secondly, in order to achieve a desired friction as after the assembling, the tapered inner surface 43 and the tapered outer surface 44 have to be machined to a high accuracy. Specifically, if the angle made by the two tapered surfaces 43, 44 is too large, the retaining ring 36 cannot be held by the friction and moves away, becoming unable to provide the expected function. For example, in the state shown in FIG. 9, it has been confirmed that the angle xcex8 between the tapered surfaces 43, 44 must be smaller than 20xc2x0 approximately. As a result of such a high machining accuracy required of each part, manufacturing cost of these has to increase.
The present invention is made to solve the above described problems, with an object to provide a fastening structure between link and pin of a crawler belt which can be assembled by simple operation at a low cost, without requiring a high machining accuracy, and thus can be manufactured at a low cost.
Now, a fastening structure of link and pin of a crawler belt according to a first invention is a fastening structure of a link and a pin in a crawler belt of a vehicle. An annular space 15 is formed between a circumferential edge of an opening of a pin insertion hole 5 of a link 2 and an outer end portion of a pin 1 to be inserted in the pin insertion hole 5, and a retaining ring 3 is disposed in the space 15 whereby preventing relative, disengaging movement of the pin 1 toward a side away from the opening. The structure is characterized in that one of the circumferential edge of the opening of the pin insertion hole 5 of the link 2 and the outer end portion of the pin 1 is formed with a tapered pressure receiving surface 8 having a diameter gradually decreasing in an axially inward direction, the other is formed with a pressing portion 7, and the retaining ring 3 is formed with a friction surface 9 to be press-contacted to the pressure receiving surface 8 by a force from the pressing portion 7 upon development of the relative movement in the disengaging direction. It should be noted here that the pressing portion 7 may be an edge portion as in the first embodiment through the third embodiment, or may be a tapered pressure receiving surface as in the fourth embodiment. In this case, a portion of the retaining ring 3 contacted by the pressing portion 7, (a pressed surface), is formed as a friction surface as in the fourth embodiment.
According to the fastening structure between link and pin of a crawler belt provided by the first invention, the following function is performed. First, if the pin 1 makes a relative movement in the disengaging direction toward the side away from the opening, then the pressing portion 7 of the link 2 contacts the pressed surface 10 of the retaining ring 3, and the friction surface 9 of the retaining ring 3 press-contacts the tapered, pressure receiving surface 8. Under this state, the ring 3 is under a force acting in the disengaging direction. This force F1 can be divided into a component force F2 acting vertically to the pressure receiving surface 8 and another component force F3 acting along the pressure receiving surface 8. Based on this, the relative, disengaging movement toward the side away from the opening is prevented by selecting a condition that makes friction generated by the component force F2 acting vertically to the pressure receiving surface 8 greater than the component force F3 acting along the pressure receiving surface 8. Specifically, the pressure receiving surface 8 slanted axially inward is given a slant angle xcex1 that satisfies the above mentioned relationship xcexcxc2x7F2 greater than F3 (where xcexc represents friction coefficient), thereby preventing the pin from relative, disengaging movement out of the link toward the side away from the opening.
According to the fastening structure of link and pin of a crawler belt provided by the first invention, the retaining ring 3 contacts the pressure receiving surface 8 via its friction surface 9. For this reason, the retaining ring 3 has a greater area of contact with the pressure receiving surface 8 than in the prior art. Therefore, elastic restoring force of the retaining ring 3 alone can generate sufficient initial friction. Thus, there no longer is the need for the operation of inwardly driving the retaining ring 3 during the assembly. As a result, there no longer is the need for the special jig and the pressing apparatus for driving the ring 3, and as a result, it becomes possible to reduce cost necessary for the assembling operation.
Further, the slant angle xcex1 of the pressure receiving surface 8 slanting axially inward should only satisfy the above mentioned relationship xcexcxc2x7F2 greater than F3. Thus, there no longer is the need for high machining accuracy in the angle of the tapered surface as is in the prior art, and therefore it becomes possible to reduce relevant manufacturing cost.
A fastening structure between link and pin of a crawler belt according to a second invention is characterized in that the retaining ring 3 includes a pressed surface 10 contacted by the pressing portion 7, and the friction surface 9, whereas the pressed surface 10 and the friction surface 9 are farther away from each other in an outward direction.
According to the fastening structure between link and pin of a crawler belt provided by the second invention, the friction surface 9 and the pressed surface 10 of the retaining ring 3 are farther away from each other in the outward direction. Therefore, even if there is inconsistency in an engaging dimension between the pressing portion 7 and the pressure receiving surface 8 resulting from machining error, assembling error and so on, the friction surface 9 and the pressed surface 10 of the retaining ring 3 can make respective engagements at various dimensions, which means an engageable range for the two is increased. As a result, it becomes possible to allow for more generous tolerance in the shape and dimensions of the pressing portion 7 in the link 2 and of the pressure receiving surface 8 in the pin 1 than in the prior art.
A fastening structure between link and pin of a crawler belt according to a third invention is characterized in that the retaining ring 3 has a square section.
According to the fastening structure between link and pin of a crawler belt provided by the third invention, since the retaining ring 3 has a square section, manufacture thereof becomes easy, and can be embodied at a low cost.
A fastening structure between link and pin of a crawler belt according to a fourth invention is characterized in that the pressing portion 7 is formed like an edge.
According to the fastening structure between link and pin of a crawler belt provided by the fourth invention, by making one of the circumferential edge of the opening of the pin insertion hole 5 of the link 2 and the outer end portion of the pin 1 as the edge-like pressing portion 7, it becomes possible to allow for even more generous tolerance in the shape and dimensions of the pressing portion 7 in the link 2 and of the pressure receiving surface 8 in the pin 1 than in the case where both are made as tapered pressure receiving surfaces.
A fastening structure between link and pin of a crawler belt according to a fifth invention is a fastening structure of a link and a pin in a crawler belt of a vehicle. An annular space is formed between a circumferential edge of an opening of a pin insertion hole 5 of a link 2 and an outer end portion of a pin 1 inserted in the pin insertion hole 5, and a retaining ring 3 is disposed in the space 15 whereby preventing relative disengaging movement of the pin 1 toward a side away from the opening. The structure is characterized in that one of the circumferential edge of the opening of the pin insertion hole 5 of the link 2 and the end portion of the pin 1 is formed with a tapered pressure receiving surface 8 having a diameter gradually decreasing in an axially inward direction, the other is formed with an edge-like pressing portion 7, and the retaining ring 3 press-contacts each of the pressing portion 7 and the pressure receiving surface 8.
According to the fastening structure between link and pin of a crawler belt provided by the fifth invention, the following function is performed. First, in an assembling step, when the retaining ring 3 is disposed in the space 15 and the retaining ring 3 is pushed inward, then the edge-like pressing portion 7 is press-contacted to the retaining ring 3 whereas the retaining ring 3 is press-contacted to the tapered pressure receiving surface 8. Under this state, a vicinity of the contacting portion in the retaining ring 3 is elastically deformed by the pressure, providing a surface on the retaining ring 3 on the side facing the pressure receiving surface 8. In other words, a friction surface 9 contacting the pressure receiving surface 8 is created. Therefore, if the pin 1 tends to make relative movement in the disengaging direction toward the side away from the opening under this state, then the retaining ring 3 comes under a force F1 acting in the disengaging direction. This force F1 can be divided into a component force F2 acting vertically to the pressure receiving surface 8 and another component force F3 acting along the pressure receiving surface 8. Based on this, the relative, disengaging movement of the pin toward the side away from the opening is prevented by selecting a condition that makes friction generated by the component force F2 acting vertically to the pressure receiving surface 8 greater than the component force F3 acting along the pressure receiving surface 8. Specifically, the pressure receiving surface 8 slanted axially inward is given a slant angle xcex1 that satisfies the above mentioned relationship xcexcxc2x7F2 greater than F3 (where xcexc represents friction coefficient), thereby preventing the pin from relative, disengaging movement out of the link toward the side away from the opening.
According to the above described fastening structure between link and pin of a crawler belt provided by the fifth invention, the retaining ring 3 has the friction surface 9 provided by the assemblage, making contact with the pressure receiving surface 8. Therefore, the retaining ring 3 has a greater area of contact with the pressure receiving surface 8 than in the prior art, making possible to obtain sufficient initial friction. Further, since one of the circumferential edge of the opening of the pin insertion hole 5 of the link 2 and the outer end portion of the pin 1 is made into the edge-like pressing portion 7, the retaining ring 3 receives the pressure at a point, and thus it becomes possible to perform the assembling operation more easily, using less pressing force than in the case where the two members are each formed with a tapered surface, i.e. than in the case where the pressure is received on a surface. As a result, operating efficiency in the assembling operation can be improved.
Further, the slant angle xcex1 of the pressure receiving surface 8 slanting axially inward should only satisfy the above mentioned relationship xcexcxc2x7F2 greater than F3. Thus, there no longer is the need for high machining accuracy in the angle of the tapered surface as is in the prior art, and therefore it becomes possible to reduce relevant manufacturing cost. Further, since one of the link 2 and the pin has the edge-like pressing portion 7, it becomes possible to allow for more generous tolerance in the shape and dimensions of the link 2 and of the pin 1 than in the case where both are made as tapered pressure receiving surfaces.
A fastening structure between link and pin of a crawler belt according to a sixth invention is characterized in that the retaining ring 3 has a circular section.
According to the fastening structure between link and pin of a crawler belt of the sixth invention, since the retaining ring 3 has a circular section, manufacture thereof becomes easy, making possible to embody at a low cost.